High performance thermoplastic vulcanizate

ABSTRACT

A high performance thermoplastic hose useful as a power steering hose, the high performance thermoplastic hose comprising a high performance engineering thermoplastic such as polyurethane and a chlorine-containing polyolefin such as chlorinated polyethylene, chlorinated polypropylene, chlorinated copolymers containing ethylene and propylene, chlorosulfonated polyethylene, chlorosulfonated polypropylene, chlorosulfonated copolymers of ethylene and propylene or mixture thereof, is disclosed. Also disclosed are a method for manufacturing the high performance thermoplastic hose, and a thermoplastic vulcanizate capable of resisting chemical attack and withstanding temperatures up to about 300° F.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a thermoplastic vulcanizateprepared from a high performance engineering thermoplastic polymer suchas polyurethane and a chlorosulfonated polyolefin and/or a chlorinatedpolyolefin; to a high performance hose such as a power steering hoseconstructed from such thermoplastic vulcanizate material; and to amethod for the manufacture of such high performance hoses.

[0003] 2. Description of the Prior Art

[0004] Hoses, particularly curved hoses, typically, are manufactured bypositioning a pre-cut length of uncured hose over a curved mandrel andthen heating the mandrel and curing the hose so that the hose retainsits desired shape. The hose may solely be an elastomeric tube or it maybe surrounded or have incorporated therein a twined reinforcement.Optionally, a cover may surround the hose. Typically, the hose is madeby extruding a tube of heat curable elastomer. The hose is then placedover the mandrel which is heated to cure the inner layer next to themandrel. The cured hose is then removed from the mandrel while themandrel is hot to facilitate easy removal of the cured hose from themandrel. One such method is described in U.S. Pat. No. 4,537,736 toPeltzman et al. Such rubber hoses have been used in a wide variety ofapplications such as fuel feed hoses, torque converter hoses, airconditioner hoses, power steering hoses, etc. However, in general,rubber surfaces do not exhibit high resistance to chemical attack andprior art attempts have failed to increase the chemical resistancebeyond certain limits. For example, U.S. Pat. No. 5,476,121 to Yoshikawaet al discloses rubber hoses having improved barrier and flexibilityperformance by providing an inner tube of a synthetic resin having anouter peripheral surface, forming a thin film of silver or a silver basealloy on the outer surface of the inner tube, and heat curing a rubberlayer to the thin film through an adhesive layer.

[0005] High performance hoses such as power steering hoses require highresistance to both chemical and temperature degradation. At present,power steering hoses and other high performance hoses are made fromcompounded elastomers such as a chlorinated polyethylene, achlorosulfonated polyethylene or similar materials capable ofwithstanding temperatures up to 300° F. and the chemical effects ofpower steering fluids. Chlorine-containing polyolefins includingchlorinated polyethylene and chlorosulfonated polyethylene generallypossess good mechanical properties, good compression set, good lowtemperature flexibility and good dynamic fatigue resistance. Thesematerials also exhibit excellent aging, weathering, chemical and ozoneresistance due to their saturated backbones. However, in order towithstand high temperatures of about 300° F. and chemical resistance topower steering fluids, hoses constructed of such materials must be builtand vulcanized on a mandrel and then removed from the mandrel foradditional processing. A method for the manufacture of power steeringhose on a mandrel is further described in U.S. Pat. No. 3,972,757 toDerderian et al. In view of the cost associated with manufacturing highperformance hoses such as power steering hoses, it is desirable toprovide materials having the desired characteristics but which areeasily formable without the use of a mandrel while providing improvedperformance and reduced overall costs.

[0006] U.S. Pat. No. 5,683,773 to Kemper teaches an automotive hosewhere the inner tube or, preferably, the cover portion is formed of anelastomer comprising a chlorinated polyethylene-based elastomer orpolyether-based elastomer stabilized with barium sulfate.

SUMMARY OF THE INVENTION

[0007] In accordance with the present invention, high performance hosessuch as power steering hoses are prepared from a thermoplasticvulcanizate (TPV) using a chlorinated polyolefin and/or achlorosulfonated polyolefin with polyurethane or one or more similarhigh performance engineering thermoplastic materials. There is no knownthermoplastic material, when used alone, which will withstand thetemperature and the fluid of power steering applications for prolongedperiods of time. However, it has been found that such thermoplasticmaterials typically have high green strength, high tear strength andgood abrasion resistance and when used with the chlorinated polyolefinsand/or chlorosulfonated polyolefins in accordance with the presentinvention, can be employed in the manufacture of high performance hosesuch as power steering hose. The high performance engineeringthermoplastic material can be crosslinked in the matrix during extrusionof the thermoplastic vulcanizate by adding any suitable crosslinkingagent to the vulcanizate. Chlorosulfonated polyethylene or a mixture ofchlorinated polyethylene and chlorosulfonated polyethylene compoundedwith polyurethane has been found to be particularly useful in thepreparation of the thermoplastic vulcanizate of the present invention.The thermoplastic vulcanizate of the present invention exhibits thefollowing advantages over the prior art:

[0008] (1) Vulcanization is not required;

[0009] (2) The material can be extruded to close tolerance without amandrel;

[0010] (3) The material is light weight due to high modulus, and lessmaterial is needed;

[0011] (4) The material is recyclable;

[0012] (5) The material is easily formed into hoses;

[0013] (6) The material has better abrasion and tear resistance thanprior art materials; and

[0014] (7) The material can be made at a lower overall cost with betterperformance than prior art materials.

[0015] It is one aspect of the present invention to provide a lightweight thermoplastic vulcanizate material having improved abrasion andtear resistant characteristics for use in the manufacture of highperformance hoses such as power steering hoses.

[0016] It is another aspect of the invention to provide a highperformance hose such as a power steering hose constructed from suchthermoplastic vulcanizate material.

[0017] It is yet another aspect of the invention to provide a method formanufacturing the high performance hose which eliminates the processingsteps required for prior art elastomeric hose.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The thermoplastic vulcanizate material of the present inventioncomprises a chlorinated polyolefin and/or a chlorosulfonated polyolefinand a high performance engineering thermoplastic material such aspolyurethane. It has been found that the present thermoplasticvulcanizate is particularly useful in the manufacture of highperformance hoses. In a preferred aspect of the invention, thethermoplastic vulcanizate is used as the matrix for the construction ofpower steering hoses in automobiles.

[0019] The chlorine-containing component useful in the present inventionis a chlorinated polyolefin or a chlorosulfonated polyolefin andincludes, but is not limited to, chlorinated polyethylene, chlorinatedpolypropylene, chlorosulfonated polyethylene, chlorosulfonatedpolypropylene, chlorinated copolymers of ethylene and propylene,chlorosulfonated copolymers of ethylene and propylene and mixturesthereof.

[0020] The chlorine-containing polyolefin component of the thermoplasticvulcanizate is, typically, chlorosulfonated polyethylene although otherchlorosulfonated polyolefins such as chlorosulfonated polypropylene andchlorosulfanated copolymers of ethylene and propylene may be used. Forthe purpose of this invention, the term copolymer is intended to includetwo or more monomers such as ethylene, propylene, butenes, etc. Hypalon,a chlorosulfonated polyethylene available from DuPont has been found tobe particularly useful in the present invention.

[0021] The amount of chlorinated polyolefin and/or chlorosulfonatedpolyolefin in the thermoplastic vulcanizate is typically in the range ofabout 10 to 90% by weight of the thermoplastic vulcanizate, andpreferably, about 30 to 70% by weight of the thermoplastic vulcanizate.While each of the chlorinated polyolefin and the chlorosulfonatedpolyolefin can be used with the exclusion of the other in the presentinvention, it has been found that a combination of the chlorinatedpolyolefin and the chlorosulfonated polyolefin provides excellentresults as well. When both chlorinated polyolefin and chlorosulfonatedpolyolefin are present in the thermoplastic vulcanizate, the ratio ofchlorinated polyethylene to chlorosulfonated polyethylene typically willbe about 3:1 to 1:3, preferably about 2:1 to 1:2 and most preferablyabout 1:1. As indicated earlier Hypalon, a chlorosulfonated polyethylenemanufactured by DuPont, has been found to be particularly useful as thechlorosulfonated component.

[0022] The high performance engineering thermoplastic component of thethermoplastic vulcanizate can be any of the high performance engineeringthermoplastic materials commonly used in the industry. Examples of suchhigh performance engineering plastic materials include polyurethanes;and may include polyethers such as polyacetal, polyphenylene oxide,polyether ketone, polyphenylene sulfide, etc.; polyamides such as nylon,e.g., nylon 6, nylon 66, nylon 4, nylon 11, nylon 12, nylon 6/12, nylon6/10, etc.; highly aromatic polyamides such as Kevlar and Nomex whichare available from DuPont; polyesters, such as polyethyleneterephthalate; copolyesters such as Hytrel available from DuPont;polyimides, such as polyether imides, polyimide imides,polybismaleimides; polysulfones and the like. These resins may be usedalone or as a blend of two or more of the resins. Preferably, thethermoplastic component is polyurethane. The amount of the highperformance engineering thermoplastic component present in thethermoplastic vulcanizate will be that which is sufficient to providethe improved characteristics of the vulcanizate. The amount of the highperformance engineering thermoplastic component can be in the range ofabout 90 to 10% by weight based on the weight of the thermoplasticvulcanizate and, preferably, about 70 to 30% by weight based on theweight of the thermoplastic vulcanizate.

[0023] Optionally, the high performance engineering thermoplasticmaterial may be crosslinked in the thermoplastic vulcanizate matrix byadding a suitable crosslinking agent to the vulcanizate prior to orduring extrusion of the high performance hose. The thermoplasticvulcanizate of the present invention may be crosslinked withconventional crosslinking systems such as peroxides, e.g., dicumylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane,2,5-dimethyl-2,5-di(t-butylperoxy) hexyne-3, 1,1-bis(t-butylperoxyne)-3,t-butylperoxybenzoate, and the like. It is believed that thethermoplastic vulcanizate of the present invention may also becrosslinked with polyols such as aromatic and cyclic polyols, e.g.,hexafluoroisopropylidene-bis-(4-hydroxyphenyl) hydroquinone,isopropylidene-bis-(4-hydroxyphenyl), etc.; polyamines such ashexamethylenediamine carbamate, alicyclic diamine carbamate,dicinnamilidene hexamethylenediamine, and the like; cyanurates such astriallyl cyanurate (TAC); isocyanurates such as triallyl isocyanurate(TAIC); and the like; isocyanates and diisocyanates, such asdiphenylmethane diisocyanate. Crosslinking agents containing at leasttwo and preferably more than two functional groups such as TAC, TAIC,isocyanates, mixtures of isocyanates and polymeric isocyanates havingfunctionality of more than 2.0 are found to be very useful. In somecases a conventional crosslinking accelerator may be used to provideimproved results. Typically, the crosslinking agent will be added to thevulcanizate in an amount of about 1 to 10% and preferably about 1 to 5%by weight, based upon the weight of the vulcanizate.

[0024] The thermoplastic vulcanizate of the invention is particularlyuseful in the manufacture of high performance hoses such as powersteering hoses and, in addition to being able to withstand the adverseeffects of high temperature and chemical degradation, the presentmaterials do not require vulcanization on a mandrel as is commonlyrequired in the prior art; they can be extruded to close tolerance; theyare light weight and recyclable, and they have better abrasion and tearresistance than prior art materials.

[0025] Other additives such as carbon black; silica; calcium carbonate;clay; diatomaceous earth, mica; heat stabilizers, e.g., metal oxidessuch as magnesium oxide, organotin compounds, and mixed metal salts;antioxidants; lubricants; plasticizers, softeners, processing aids; andthe like may be incorporated into the thermoplastic vulcanizate inamounts generally known in the art to provide the desired effect forwhich they are added.

[0026] According to the invention, the high performance hose can beformed to close tolerance by a simple extrusion process wherein thethermoplastic vulcanizate is prepared by dynamic vulcanization where theelastomeric component is vulcanized during mixing.

[0027] The following examples are submitted for the purpose of furtherillustrating the present invention and are not intended as a limitationon the scope thereof.

EXAMPLE

[0028] Thermoplastic vulcanizates (TPV) are made with polyurethane andchlorosulfonated polyethylene or a mixture of chlorosulfonatedpolyethylene and chlorinated polyethylene by dynamic vulcanizationmethod wherein the vulcanizate contains about 30 to 70% polyurethane andabout 70 to 30% chlorosulfonated polyethylene or a mixture ofchlorosulfonated polyethylene and chlorinated polyethylene wherein theratio of chlorosulfonated polyethylene to chlorinated polyethylene isabout 3:1 to 1:3. The compounds are extruded to a tight tolerance tube,braided with or without adhesive to get proper adhesion and then coveredwith the same or different composition TPV using the same basematerials. The hoses are then cut into desired length, formed internallyor externally by heating the fixture in a continuous line passingthrough an oven, and cooling the fixture by a suitable method,preferably by dipping or spraying using cold water.

[0029] Although the invention has been described and exemplified hereinwith respect to the preferred embodiments thereof, it is to beunderstood that the invention is not limited to the embodiments, andthat variations can be made therein without departing from the scope ofthe invention.

What is claimed is:
 1. A high performance thermoplastic hose useful as apower steering hose, said high performance thermoplastic hose comprisinga high performance engineering thermoplastic material and achlorine-containing polyolefin.
 2. The high performance thermoplastichose of claim 1 wherein said high performance engineering thermoplasticpolymeric material is selected from the group consisting ofpolyurethane, polyamide, polyether, polyester, copolyester, polyimides,polysulfones, and mixtures thereof.
 3. The high performancethermoplastic hose of claim 2 wherein said high performance engineeringthermoplastic polymeric material is polyurethane.
 4. The highperformance thermoplastic hose of claim 1 wherein saidchlorine-containing polyolefin is selected from the group consisting ofchlorinated polyethylene, chlorinated polypropylene, chlorinatedcopolymers containing ethylene and propylene, chlorosulfonatedpolyethylene, chlorosulfonated polypropylene, chlorosulfonated polymersof ethylene and propylene, and mixtures thereof.
 5. The high performancethermoplastic hose of claim 4 wherein said chlorine-containingpolyolefin is chlorosulfonated polyethylene.
 6. The high performancethermoplastic hose of claim 4 wherein said chlorine-containingpolyolefin is a mixture of chlorinated polyethylene and chlorosulfonatedpolyethylene.
 7. The high performance thermoplastic hose of claim 6wherein said chlorinated polyethylene and said chlorosulfonatedpolyethylene in said mixture are present in a ratio of chlorinatedpolyethylene to chlorosulfonated polyethylene of about 3:1 to 1:3. 8.The high performance thermoplastic hose of claim 1 wherein said highperformance engineering thermoplastic material is present in an amountof about 30 to 70% by weight of said high performance thermoplastic hoseand said chlorine-containing polyolefin is present in an amount of about70 to 30% by weight of said high performance thermoplastic hose.
 9. Amethod for manufacturing a high performance thermoplastic hose capableof resisting chemical attack and withstanding temperatures up to about300° F. for use as a power steering hose, said method comprisingextruding a thermoplastic vulcanizate through an extruder at atemperature of about 380° F. wherein said thermoplastic vulcanizatecomprises a high performance engineering thermoplastic material and achlorine-containing polyolefin.
 10. The method of claim 9 wherein saidhigh performance engineering thermoplastic material is selected from thegroup consisting of polyurethane, polyamide, polyether, polyester,copolyester, polyimide, polysulfone and mixtures thereof.
 11. The methodof claim 10 wherein said high performance engineering thermoplasticmaterial is polyurethane.
 12. The method of claim 9 wherein saidchlorine-containing polyolefin is selected from the group consisting ofchlorinated polyethylene, chlorinated polypropylene, chlorinatedcopolymers containing ethylene and propylene, chlorosulfonatedpolyethylene, chlorosulfonated polypropylene, chlorosulfonatedcopolymers containing ethylene and propylene, and mixtures thereof. 13.The method of claim 12 wherein said chlorine-containing polyolefin ischlorosulfonated polyethylene.
 14. The method of claim 12 wherein saidchlorine-containing polyolefin is a mixture of chlorinated polyethyleneand chlorosulfonated polyethylene.
 15. The method of claim 14 whereinsaid chlorinated polyethylene and said chlorosulfonated polyethylene arepresent in said mixture in a ratio of chlorinated polyethylene tochlorosulfonated polyethylene of about 3:1 to 1:3.
 16. The method ofclaim 9 wherein said mixture comprises about 30 to 70% by weight highperformance engineering thermoplastic material and about 70 to 30% byweight chlorine-containing polyolefin.
 17. The method of claim 9 whereinsaid method further comprises the steps of adding a crosslinking agentto said thermoplastic vulcanizate.
 18. The method of claim 17 whereinsaid crosslinking agent is a peroxide, an isocyanate havingfunctionality of more than 2.0, or a cyanurate or isocyanuratecontaining two or more functional groups.
 19. The method of claim 17wherein said crosslinking agent is added in an amount of up to about 5%by weight of said thermoplastic vulcanizate.
 20. A thermoplasticvulcanizate capable of resisting chemical attack and withstandingtemperatures up to about 300° F., said vulcanizate comprising a highperformance engineering thermoplastic material and a chlorine-containingpolyolefin.
 21. The thermoplastic vulcanizate of claim 20 wherein saidhigh performance engineering thermoplastic material is selected from thegroup consisting of polyurethane, polyamide, polyether, polyester,copolyester, polyimide, polysulfone, and mixtures thereof.
 22. Thethermoplastic vulcanizate of claim 21 wherein said high performanceengineering thermoplastic material is polyurethane.
 23. Thethermoplastic vulcanizate of claim 16 wherein said chlorine-containingpolyolefin is selected from the group consisting of chlorinatedpolyethylene, chlorinated polypropylene, chlorinated copolymerscontaining ethylene and propylene, chlorosulfonated polyethylene,chlorosulfonated polypropylene, chlorosulfonated copolymers containingethylene and propylene, and mixtures thereof.
 24. The thermoplasticvulcanizate of claim 23 wherein said chlorine-containing polyolefin ischlorosulfonated polyethylene.
 25. The thermoplastic vulcanizate ofclaim 23 wherein said chlorine-containing polyolefin is a mixture ofchlorinated polyethylene and chlorosulfonated polyethylene.
 26. Thethermoplastic vulcanizate of claim 25 wherein said chlorinatedpolyethylene and said chlorosulfonated polyethylene in said mixture arepresent in a ratio of chlorinated polyethylene to chlorosulfonatedpolyethylene of about 3:1 to 1:3.
 27. The thermoplastic vulcanizate ofclaim 20 wherein said high performance engineering thermoplasticmaterial is present in an amount of about 30 to 70% by weight of saidthermoplastic vulcanizate and said chlorine-containing polyolefin ispresent in an amount of about 70 to 30% by weight of said thermoplasticvulcanizate.